The Cerna is a river in Romania. The Cerna has its source on the south-east side of the Godeanu Mountains and flows into the Danube near the town Orșova. The upper reach of the river is sometimes called Cernișoara. With a basin of 1433 square km and a length of 84 km, it carves an erosive tectonic valley with numerous gorges, quite deep sometimes. There is a man-made lake on it (Tierna), just before it crosses the Băile Herculane spa, to perpetuate the old toponimic od Dierna. The upper course of the Cerna is part of the Domogled-Valea Cernei national park.